spasm

Short definition from Wiktionary

Noun

1. 1
   A sudden, involuntary contraction of a muscle, a group of muscles, or a hollow organ.
2. 2
   A violent, excruciating seizure of pain.
3. 3
   A sudden and temporary burst of energy, activity, or emotion.

Verb

1. 1
   To produce and undergo a spasm or series of spasms.